DESCRIPTION: The purpose of the proposed studies is to expand an animal model of tinnitus, which has been developed by the investigator and used to evaluate salicylate-induced tinnitus, to the more usual cases of tinnitus related to sensorineural hearing loss, particularly those caused by excessive exposure to noise. In this application, studies of the peripheral representation of tinnitus after noise exposure and their central correlates are proposed. A behavioral paradigm utilizing an extinction of conditioned suppression technique will be used to assess the presence of tinnitus-like perceptions in rats after exposures to noise which produce permanent hearing loss and damage the cochlea. The functional properties of the cochlea will be assessed by measuring distortion product otoacoustic emissions (DPOAEs) and N1 of the auditory brainstem response (ABR) in rats before and after pure-tone exposures To assess the central representation of tinnitus, spontaneous single unit activity in the inferior colliculus will be monitored in animals which do and not exhibit tinnitus-like behavior. Groups of animals without additional manipulations and with conductive hearing loss will serve as controls. The correlation of behavioral, DPOAE/ABR, and single unit data may elucidate the basis of potential physiological mechanisms of this common type of tinnitus.